Cassette

ABSTRACT

A cassette having a transmission plate disposed on radiation exposure side and transmitting radiation, and a housing part disposed on opposite to the radiation exposure side, the cassette comprises a radiation detector that is disposed between the transmission plate and the housing part, in which material of the housing part contains 5 mass % or more and 25 mass % or less of lithium.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of application Ser. No. 15/615897filed on Jun. 7, 2017, which claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2016-126604, filed on Jun. 27, 2016.Each of the above application(s) is hereby expressly incorporated byreference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a cassette.

2. Description of the Related Art

In the related art, radiation detection cassettes have been widely usedin radiation imaging, such as X-ray imaging. The radiation detectioncassettes are portable radiation detection devices including arectangular housing, and a radiation detector that is housed within thehousing and detects radiation transmitted through a subject.

The radiation detection cassettes are capable of being used by beingattached to a stationary imaging stand where a subject is imaged in astanding posture or lying posture. In addition, the radiation detectioncassettes are used by being put on a bed in order to image a site (forexample, limbs) where imaging is difficult in the stationary imagingstand or by being carried by the subject himself or herself.Additionally, in order to image elderly people under recuperation athome or emergency cases due to an accident, disaster, or the like, theradiation detection cassettes may be used by being carried to theoutside of hospitals without equipment of the imaging stand.

SUMMARY OF THE INVENTION

Here, the housing of the related-art radiation detection cassettesinclude a transmission plate that is arranged on a radiation exposureside and that allows radiation to be transmitted therethrough, and aback surface plate that is arranged to face the transmission plate. Forexample, an Mg alloy consisting of Mg (magnesium), Al (aluminum), and Zn(zinc) is used as the back surface plate.

Since the radiation detection cassettes are carried by a person, it isdesirable that the radiation detection cassettes are light-weight, andit is desirable to use an alloy containing Mg and Li (lithium) whosespecific gravity is smaller than that of the above Mg alloy (forexample, refer to JP2011-084818A).

Meanwhile, recesses partitioned by ribs or the like are formed in aninner surface of the back surface plate. In a case where the recessesare formed by cutting work, it is necessary to perform grooving using anend mill or the like on a material in which no recesses are formed.

However, in a case where such grooving is performed, since an escapeplaces for the heat of a blade of the end mill is small, the blade isheated, and the alloy containing Mg and Li whose melting point is lowerthan the above Mg alloy deposits on the blade of the end mill. As aresult, the recess cannot be formed appropriately.

In view of the above problems, an object of the invention is to providea cassette having a transmission plate disposed on radiation exposureside and transmitting radiation, and a housing part disposed on oppositeto the radiation exposure side, the cassette comprises a radiationdetector that is disposed between the transmission plate and the housingpart, material of the housing part contains 5 mass % or more and 25 mass% or less of Li.

Means for Solving the Problems

According to an aspect of the invention, there is provided a cassettehaving a transmission plate disposed on radiation exposure side andtransmitting radiation, and a housing part disposed on opposite to theradiation exposure side. The cassette comprises a radiation detectorthat is disposed between the transmission plate and the housing part, inwhich material of the housing part contains 5 mass % or more and 25 mass% or less of Li.

Additionally, the cassette of the above aspect of the invention, thehousing part may have recesses on a surface on the radiation detectorside.

Additionally, the cassette of the above aspect of the invention, thecassette further comprises a radiation shield plate that is provided onthe side opposite to the radiation exposure side with respect to theradiation detector; and a support that is provided on the side oppositeto the radiation exposure side with respect to the radiation shieldplate, and that supports the radiation shield plate. The support may befixed to the housing part.

Additionally, the cassette of the above aspect of the invention, thecassette further comprises a support that is provided on the sideopposite to the radiation exposure side with respect to the radiationdetector, and that supports the radiation detector. The support may befixed to the housing part. The support and the housing part may directlyface each other.

Additionally, the cassette of the above aspect of the invention, thematerial of the housing part may further contain Al.

Advantage of the Invention

According to the invention, a cassette having a transmission platedisposed on radiation exposure side and transmitting radiation, and ahousing part disposed on opposite to the radiation exposure side, thecassette comprises a radiation detector that is disposed between thetransmission plate and the housing part, in which material of thehousing part contains 5 mass % or more and 25 mass % or less of Li canbe provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating the external appearance whenan embodiment of a radiation detection cassette of the invention is seenfrom a radiation exposure side.

FIG. 2 is a perspective view illustrating the external appearance whenthe embodiment of the radiation detection cassette of the invention isseen from a side opposite to the radiation exposure side.

FIG. 3 is a view of the radiation detection cassette illustrated in FIG.2 as seen from arrow A direction.

FIG. 4 is a view of the radiation detection cassette illustrated in FIG.2 as seen from arrow B direction.

FIG. 5 is a perspective view of a back housing part formed of an alloycontaining Mg and Li as seen from an inner surface (a surface on aradiation detector side) side.

FIG. 6 is a flowchart for explaining an embodiment of a method formanufacturing a housing of the radiation detection cassette of theinvention.

FIG. 7 is a view illustrating an insertion screw provided in a femalethread part.

FIG. 8 is a C-C line cross-sectional view of the radiation detectioncassette illustrated in FIG. 1.

FIG. 9 is a cross-sectional view illustrating another embodiment of theradiation detection cassette of the invention.

FIG. 10 is a cross-sectional view illustrating still another embodimentof the radiation detection cassette of the invention.

FIG. 11 is a view illustrating an example of a radiation shield that isattachably and detachably configured with respect to the housing of theradiation detection cassette.

FIG. 12 is a cross-sectional view illustrating a schematic configurationaround a recess formed in the back housing part.

FIG. 13 is a view illustrating still another embodiment of a frame bodythat constitutes the housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, an embodiment of a method for manufacturing a housing of aradiation detection cassette of the invention will be described indetail, referring to the drawings. Although the invention has featuresin the method for manufacturing a housing of a radiation detectioncassette, the configuration of a radiation detection cassette having ahousing manufactured using the embodiment of the manufacturing method ofthe invention will first be described. FIG. 1 is a perspective viewillustrating the external appearance when the radiation detectioncassette 1 having the housing manufactured by the manufacturing methodof the present embodiment is seen from a radiation exposure side, andFIG. 2 is a perspective view illustrating the external appearance whenthe radiation detection cassette 1 is seen from a side opposite to theradiation exposure side. Additionally, FIG. 3 is a view of the radiationdetection cassette 1 illustrated in FIG. 2 as seen from arrow A, andFIG. 4 is a view of the radiation detection cassette 1 illustrated inFIG. 2 as seen from arrow B.

The radiation detection cassette 1 of the present embodiment includes aradiation detector 20, and a housing 10 that houses the radiationdetector 20.

As illustrated in FIGS. 1 to 4, the housing 10 is formed in arectangular shape, and includes a transmission plate 11 arranged on theradiation exposure side, a back housing part 12 having a surface portionopposite to the radiation exposure side, and a frame body 13.

The transmission plate 11 is formed of a carbon material with a hightransitivity of radiation, and is lightweight and high-rigidity.

The back housing part 12 is formed of an alloy containing Mg and Li andcontaining 0.1 mass % or more of Li. Since the alloy containing Mg andLi has a smaller specific gravity than an Mg alloy (Al 3%, Zn 1%, and Mg96%) used as a material of a back housing part of the related-artradiation detection cassette, weight reduction of the radiationdetection cassette 1 can be achieved. Additionally, the alloy containingMg and Li has radiotransparency higher than the Mg alloy. Hence,generation of scattered radiation resulting from thickness structures,such as ribs formed on an inner surface (a surface on a radiationdetector side) of the back housing part 12 can be suppressed.Accordingly, a radiation shield plate containing lead provided withinthe related-art radiation detection cassette to absorb the abovescattered radiation can be thinned or omitted, and the weight reductioncan be further achieved. As the alloy containing Mg and Li, for example,an alloy of 14 mass % of Li(s), 9 mass % of Al, and 77 mass % of Mg canbe used. It is preferable that the content of Li is 5 mass % or more and25 mass % or less. By making the content of Li be 25 mass % or less,manufacture can be made easy. Additionally, it is preferable that thecontent of Al is 1 mass % or more and 12 mass % or less. By making thecontent of Al be 1 mass % or more, corrosion resistance can be improved.Additionally, by making the content of Al be 12 mass % or less, theweight reduction can be achieved.

Additionally, as illustrated in FIGS. 3 and 4, the back housing part 12has a side peripheral surface part 12 a formed in a gentle inclinedsurface. By forming the side peripheral surface part 12 a with aninclined surface In this way, for example, in a case where a radiationimage of a subject that has lied oneself on a bed is captured, theradiation detection cassette 1 can be easily inserted between thesubject and the bed.

Additionally, FIG. 5 is a perspective view of the back housing part 12formed of the alloy containing Mg and Li as seen from the inner surface(the surface on the radiation detector side) side. As illustrated inFIG. 5, recesses 12 f of various shapes partitioned off by ribs 12 d areformed on an inner surface side of the back housing part 12. When suchrecesses 12 f are formed, in the related art, the recesses 12 f areformed by preparing a housing material in which no recesses 12 f areformed and performing cutting work using an end mill or the like on thehousing material.

However, in a case where the back housing part 12 is formed of the alloycontaining Mg and Li, as described above, the alloy may deposit on ablade of the end mill, so that the recesses cannot be appropriatelymachined. Thus, in the method for manufacturing a housing 10 of thepresent embodiment, the recesses 12 f are formed through a flowillustrated in a flowchart illustrated in FIG. 6.

First, a housing material that is formed of the alloy containing Mg andLi and contains 0.1 mass % or more of Li is prepared (S10). Next, arough recess pattern is formed by performing, for example, pressworking, such as hot pressing, on the surface of the housing material(S12).

Then, final recesses 12 f are shaped by performing cutting work using anend mill or the like, on the recess pattern formed by the press working(S14).

According to the manufacturing method of an above embodiment, the roughrecess pattern is shaped by performing the press working before thecutting work is performed. Thus, it is not necessary to carry outgrooving in the subsequent cutting work, and the final recesses 12 f areshaped by shouldering. Thus, the heat of the blade of the end mill canbe dissipated. Accordingly, the recesses 12 f can be appropriatelyshaped without the material depositing on the blade of the end mill.

In addition, in the present embodiment, the rough recess pattern isformed by performing the press working on the housing material beforethe cutting work. However, a working method before the cutting work isnot limited to the press working, and the rough recess pattern may beformed using electrical discharge machining or casting, such as diecasting.

Next, returning to FIG. 2, a battery housing part 12 b in which abattery 16 that supplies electrical power to the radiation detector 20is housed is formed in an outer surface of the back housing part 12. Thebattery housing part 12 b is provided by forming a recess in the outersurface of the back housing part 12. In addition, FIG. 2 illustrates astate where the battery 16 is housed in the battery housing part 12 b.

Additionally, female thread parts 12 c are formed in the back housingpart 12. A male thread 17 is fitted into each female thread part 12 c,and thereby, members, such as a support member, which is housed withinthe housing 10, are fixed to the back housing part 12.

Here, although the back housing part 12 of the present embodiment isformed of the alloy containing Mg and Li as described above, the alloycontaining Mg and Li tends to corrode electrically. That is, in a casewhere a different kind of metal comes into contact with the alloycontaining Mg and Li, the alloy containing Mg and Li with largeionization tendency corrodes if electrolytes, such as water, act. Sincemedical instruments are disinfected and sterilized, the medicalinstruments are exposed to various electrolytes, such as ethanol andperacetic acid, besides water, and electrical corrosion poses a problem.

Hence, it is desirable that the male thread 17 fitted into the femalethread part 12 c made of the alloy containing Mg and Li is made ofnonmetal, such as resin or ceramics.

Additionally, a method of preventing the electrical corrosion of thefemale thread part 12 c is not limited to this. For example, asillustrated in FIG. 7, a nonmetallic insertion screw 18 may be providedwithin the female thread part 12 c such that the male thread is fittedinto the insertion screw 18. Accordingly, even if a metallic male thread17 is used, the male thread can be prevented from coming into directcontact with the female thread part 12 c. The insertion screw 18 isgrooved in a hole so as to be engaged with the male thread 17.

Otherwise, the processing of coating the inner surface of the femalethread part 12 c with a nonmetallic material may be performed. Forexample, in a case where chemical conversion treatment or the like isperformed after the insertion screw 18 is inserted into the femalethread part 12 c, the electrical corrosion may occur between the femalethread part 12 c and insertion screw 18. However, by performing coatingprocessing on the inner surface of the female thread part 12 c asdescribed above, the electrical corrosion between the female thread part12 c and the insertion screw 18 can also be prevented.

The frame body 13 is made of a metallic frame of which four corners aresubjected to round chamfering. The frame body 13 is configured so as tobe engaged with a circumferential edge of the back housing part 12.Additionally, the transmission plate 11 is fixed to the back housingpart 12 by being engaged with the back housing part 12 in a state wherethe transmission plate 11 is fitted into the frame body 13.

Additionally, as illustrated in FIGS. 3 and 4, female thread parts 13 aare formed in the frame body 13. Each female thread part 13 a is formedthrough the frame body 13, and a male thread 15 is fitted into thefemale thread part. The male thread 15 fitted into the female threadpart 13 a of the frame body 13 reaches the back housing part 12, and isengaged with a female thread part (not illustrated) formed in the backhousing part 12. Accordingly, the frame body 13 into which thetransmission plate 11 is fitted is fixed to and integrated with the backhousing part 12. In addition, in order to prevent the electricalcorrosion resulting from contact with the female thread part of the backhousing part 12, it is desirable that the male thread 15 is also made ofnonmetal, such as resin or ceramics. Additionally, the invention is notlimited to this. However, as described above, an insertion screw 18 maybe provided in the female thread part formed in the back housing part12, or coating processing may be performed on the inner surface of thefemale thread part formed in the back housing part 12.

FIG. 8 is a C-C line cross-sectional view of the radiation detectioncassette 1 of FIG. 1. In addition, the cross-sectional view illustratedin FIG. 8 is a schematic view illustrating a schematic configuration ofthe radiation detection cassette 1, and the sizes of respective partsare not accurate.

As illustrated in FIG. 8, an outer surface of the back housing part 12is provided with a protective film 30. In the present embodiment, asdescribed above, the back housing part 12 is formed of the alloycontaining Mg and Li. Accordingly, the weight reduction of the radiationdetection cassette 1 can be achieved. On the other hand, however, sincethe radiation detection cassette 1 may be subjected to sterilization,disinfection, and the like or may be exposed to electrolyte solutions,such as a patient's blood, the corrosion resistance is required. Thealloy containing Mg and Li is less resistant against corrosion than anMg alloy containing no Li. Thus, in the present embodiment, theprotective film 30 is provided as described above. Thus, improvement inthe corrosion resistance can be achieved.

In addition, in the present embodiment, the entire outer surface of theback housing part 12 is provided with the protective film 30. However,the invention is not limited to this, and a portion of the outer surfaceof the back housing part 12 may be provided with the protective film 30.Specifically, the side peripheral surface part 12 a of the back housingpart 12 is a portion that comes into contact with a bed when theradiation detection cassette 1 is inserted between a subject and thebed. Hence, since the side peripheral surface part 12 a of the backhousing part 12, that is, a peripheral part of the surface of thehousing 10 opposite to the radiation exposure side is worn due tocontact with the bed, scratch resistance is required. Hence, it isdesirable to provide the protective film 30 at least on the sideperipheral surface part 12 a of the back housing part 12. It ispreferable that a range where the protective film 30 is provided is arange of 30 mm or more and 50 mm or less from a side end of the backhousing part 12. By providing the protective film 30 in such a range,the weight reduction can be achieved as compared to a case where theprotective film 30 is provided on the entire outer surface of the backhousing part 12. Additionally, even in a case where the protective film30 is provided on the entire outer surface of the back housing part 12,it is preferable to make the thickness of the protective film 30 in theside peripheral surface part 12 a of the back housing part 12 largerthan the thickness of the protective film 30 provided in ranges otherthan the above range.

Additionally, in the radiation detection cassette 1 of the presentembodiment, as illustrated in FIG. 8, the protective film 30 iscontinuously provided from the outer surface of the back housing part 12to an outer surface 13 b of the frame body 13. The outer surface 13 b ofthe frame body 13 on the radiation exposure side, that is, theperipheral part of the surface of the housing 10 on the radiationexposure side is a portion that comes into contact with a subject whenthe radiation detection cassette 1 is inserted between the subject and abed. Therefore, since the outer surface 13 b of the frame body 13 on theradiation exposure side is worn due to contact with the subject, thescratch resistance is required. Hence, it is desirable to provide theprotective film 30 at least on the outer surface 13 b of the frame body13 on the radiation exposure side. It is desirable that the range wherethe protective film 30 is provided is provided in ranges other than aradiation detection region. Additionally, even in a case where theprotective film 30 is provided on the entire outer surface 13 b of theframe body 13 continuously from the outer surface of the back housingpart 12, it is preferable to make the thickness of the protective film30 in the outer surface 13 b of the frame body 13 larger than thethickness of the protective film 30 provided in the other ranges.

As the protective film 30, it is desirable to use a resin sheet. Theresin sheet has easy handling and pasting. As the resin sheet, forexample, polyvinyl chloride sheets can be used. However, the protectivefilm 30 is not limited to this. For example, the protective film 30 maybe formed by performing phosphoric-acid-based or chromium-based chemicalconversion treatment. Otherwise, the protective film 30 may be formed byplating, such as electroless plating or the like, or the protective film30 may be formed by painting, such as solvent painting and powdercoating. Additionally, in order to further improve the corrosionresistance, the protective film 30 may be made to contain Al.

Next, a schematic configuration within the housing 10 of the radiationdetection cassette 1 will be described, referring to FIG. 8. Asillustrated in FIG. 8, the radiation detector 20, a radiation shieldplate 40, and a support 50 are provided within the housing 10 of theradiation detection cassette 1.

The radiation detector 20 is a rectangular detector that detectsradiation transmitted through a subject. The radiation detector 20 ofthe present embodiment includes a scintillator layer (phosphor layer) 21that converts incident radiation into visible light, and a thin filmtransistor (TFT) active matrix substrate 22 that photoelectricallyconverts of visible light emitted from the scintillator layer 21 tooutput radiation image signals. A rectangular imaging region where aplurality of pixels that accumulate electric charge according to thevisible light from the scintillator layer 21 are arrayed is formed onthe TFT active matrix substrate 22. In addition, in the presentembodiment, the TFT active matrix substrate 22 and the scintillatorlayer 21 are arranged in this order from the radiation exposure sideillustrated by arrow X in FIG. 8. However, the invention is not limitedto this. Conversely, the scintillator layer 21 and the TFT active matrixsubstrate 22 are arranged in this order from the radiation exposureside.

Additionally, in addition to the radiation detector 20, an imagingcontrol unit including a gate driver that gives a gate pulse to a gateof a TFT to switch the TFT, a signal processing circuit that converts anelectric charge accumulated in a pixel to an analog electrical signalrepresenting a radiation image to output the converted signal, and thelike is provided within the housing 10.

Additionally, in the present embodiment, a so-called indirect conversiontype radiation detector 20 that performs photoelectric conversion afterradiation is first converted into visible light is used as the radiationdetector 20. However, a so-called direct conversion type radiationdetector that directly converts radiation into an electric charge signalmay be used. Additionally, in the present embodiment, a so-called TFTreading type radiation detector using the TFT active matrix substrate 22is used. However, the invention is not limited to this. A so-calledoptical reading type radiation detector that accumulates an electriccharge with irradiation of radiation first and reads the stored chargewith irradiation of excitation light to acquire a radiation image signalmay be used.

The radiation shield plate 40 is provided on the side opposite to theradiation exposure side with respect to the radiation detector 20 withinthe housing 10, and is formed from a plate-like member containing leadwith a thickness of more than 0 mm and less than 0.1 mm.

The radiation shield plate 40 absorbs the scattered radiation resultingfrom the thickness structures, such as ribs 12 d formed on the innersurface of the back housing part 12. In the present embodiment, sincethe back housing part 12 is formed of the alloy containing Mg and Li asdescribed above, the generation of the scattered radiation itself can besuppressed. Hence, the radiation shield plate 40 can be made thinnerthan that in the related art, and the weight reduction can be achieved.In addition, in the present embodiment, lead is used as the material ofthe radiation shield plate 40. However, the invention is not limited tothis. Other radiation absorbent materials, such as Steel Use Stainless(SUS), iron, and tungsten, may be used.

The radiation shield plate 40 and the radiation detector 20 are bondedtogether, for example, using an adhesive tape or the like.

The support 50 supports the radiation detector 20 and the radiationshield plate 40, and is formed of a carbon material that allowsradiation to be transmitted through. The support 50 of the presentembodiment is fixed to the back housing part 12, and thereby, theradiation detector 20 and the radiation shield plate 40 are fixed to theback housing part 12.

In addition, in the present embodiment, the radiation shield plate 40 isprovided as described above. However, the radiation shield plate 40 maybe omitted. That is, as illustrated in FIG. 9, the support 50 and theinner surface of the back housing part 12 directly face each otherwithout providing the radiation shield plate 40. In addition, thesupport 50 and the inner surface of the back housing part 12 directlyfacing each other means that other members are not present between thesupport 50 and the inner surface of the back housing part 12.

Additionally, the configuration in which the radiation shield plate 40is not provided is not limited to the configuration illustrated in FIG.9. As illustrated in FIG. 10, the support 50 may be fixed to thetransmission plate 11 side and the radiation detector 20 may be providedat the support 50 such that the radiation detector 20 and the innersurface of the back housing part 12 directly face each other. Inaddition, the radiation detector 20 and the inner surface of the backhousing part 12 directly facing each other means that other members arenot present between the radiation detector 20 and the inner surface ofthe back housing part 12. Additionally, even in the configurationillustrated in FIGS. 7 and 8, the arrangement of the scintillator layer21 and the TFT active matrix substrate 22 may be reversed.

Additionally, in the radiation detection cassette 1 of the presentembodiment, as illustrated in FIG. 8, a waterproof structure 70 may beprovided in a gap of a portion where the circumferential edge of theback housing part 12 and the frame body 13 are engaged with each other.As the waterproof structure 70, for example, rubber packing can be used.The rubber packing is crushed by the engagement between thecircumferential edge of the back housing part 12 and the frame body 13,so that liquid-tight sealing can be made, and liquids, such as water,ethanol, and peracetic acid, which are used for disinfection andsterilization can be prevented from entering the housing 10.

Additionally, in a case where the radiation detection cassette 1 of theabove embodiment is installed and used on a bed or is installed and usedon an imaging stand for standing position imaging, the radiationtransmitted through the radiation detection cassette 1 may be reflectedto structures, such as the bed or the imaging stand, to enter theradiation detector 20 within the radiation detection cassette 1, and anartifact may be generated. Hence, in order to prevent the generation ofsuch an artifact, a radiation shield 60 containing lead may be providedat a position on the side opposite to the radiation exposure side of theradiation detection cassette 1.

It is preferable that this radiation shield 60 is made attachable anddetachable with respect to the housing 10. By adopting such aconfiguration, the radiation shield 60 can be attached to the housing 10if necessary. In a case where there is no necessity, by detaching theradiation shield 60 from the housing 10, the weight reduction of theradiation detection cassette 1 can be achieved, and carrying is alsoeasy.

FIG. 11 is a view illustrating an example of a radiation shield 60 thatis attachable to and detachable from the housing 10. The radiationshield 60 includes a radiation shield plate 62 containing lead, ahousing part 61 in which the radiation shield plate 62 is housed, and anattachment member 63. In addition, a direction of arrow X illustrated inFIG. 11 is a radiation exposure direction.

As the radiation shield plate 62, for example, a plate made of lead andhaving a thickness of 0.5 mm in the radiation exposure direction can beused. In addition, radiation absorbent materials such as a plate made ofSUS and having a thickness of 1.5 mm in the radiation exposuredirection, a plate made of tungsten and having a thickness of 1.5 mm inthe radiation exposure direction, or a plate made of iron and having athickness of 2.0 mm in the radiation exposure direction can be used.

Attachment members 63 are respectively provided on sides that faces thehousing part 61. Each attachment member 63 is turned in a direction ofarrow D about a turning shaft 63 a. Each attachment member 63 is engagedwith each of the sides that face the housing 10 of the radiationdetection cassette 1, and thereby, the radiation shield 60 is attachedto the housing 10 of the radiation detection cassette 1. FIG. 9illustrates a state where the radiation shield 60 is attached to thehousing 10, and illustrates a state of the attachment members 63 in acase where the radiation shield 60 is detached from the housing 10, by adotted line.

By attaching the attachment members 63 to the radiation shield 60 sidelike a configuration illustrated in FIG. 11, it is not necessary toperform special processing on the housing 10 of the radiation detectioncassette 1. Hence, since it is possible to be attached to any type ofhousing 10 if the size of the radiation shield 60 matches the size ofthe housing 10, it is not necessary to customize the radiation detectioncassette 1, and reduction of cost can be achieved. However, as theconfiguration in which the radiation shield 60 is attachable anddetachable, the invention is not limited to the configurationillustrated in FIG. 11, and other configurations may be adopted.

Additionally, as a method of suppressing the artifact resulting from theradiation being reflected due to the bed, the imaging stand, or thelike, the protective film 30 may be made to contain lead, and theprotective film 30 may be made to absorb the radiation reflected due tothe bed, the imaging stand, or the like. In this case, it is preferablethat the thickness of the protective film 30 is about 0.2 mm, and it ispreferable that lead contains about 50 mass %.

Additionally, in the radiation detection cassette 1 of the aboveembodiment, the protective film 30 is provided in order to give thecorrosion resistance and the scratch resistance as described above.However, it is still more preferable to make the protective film 30 hasa fireproof enclosure function. Specifically, it is preferable that theprotective film 30 contains at least one of Ca, B, and metal. Forexample, in a case where the resin sheet is used as the protective film30, a resin sheet containing at least one of Ca (calcium), B (boron),and the metal may be used. Otherwise, in a case where a paint film isused as the protective film 30, metal may be contained in a paintmaterial. As the metal contained in the protective film 30, there is,for example, Ca or the like.

Additionally, in a case where the protective film 30 is made to have thefireproof enclosure function as described above, it is desirable toprovide the protective film 30 on the entire outer surface of the backhousing part 12. However, in the radiation detection cassette 1 of thepresent embodiment, the battery housing part 12 b where a battery ishoused is formed in the back housing part 12 as described above. Thus,for example, in a case where the resin sheet is used as the protectivefilm 30, it is difficult to laminate the resin sheet uniformly withinthe battery housing part 12 b and at the peripheral part of the batteryhousing part 12 b.

Then, it is preferable to laminate separate resin sheets within thebattery housing part 12 b and at the peripheral part of the batteryhousing part 12 b. FIG. 12 is a view illustrating a sectional view,taken along arrow E-E line, of the battery housing part 12 b and itsperipheral part of the radiation detection cassette 1 illustrated inFIG. 2. In addition, in FIG. 12, the battery 16 installed within thebattery housing part 12 b is not illustrated. As illustrated in FIG. 12,it is preferable to provide a first protective film 31 at the peripheralpart of the battery housing part 12 b and provide a second protectivefilm 32 at a bottom part of the recess. It is preferable that a gap d1between an end part 31 a of the first protective film 31 and an end part32 a of the second protective film 32 adjacent to the end part 31 a ismore than 0 mm and 2 mm or less. Otherwise, the end part 31 a of thefirst protective film 31 and an end part 32 a of the second protectivefilm 32 may be made to overlap each other as seen from the side oppositeto the radiation exposure side.

Additionally, for the weight reduction of the back housing part 12, asillustrated in FIG. 12, it is preferable to form an opening 12 e at thebottom part of the battery housing part 12 b. Since the opening 12 ebeing provided in this way is not good from a viewpoint ofelectro-magnetic compatibility (EMC), in the related-art radiationdetection cassette, this opening is not provided, or the opening isneeded to be closed using a sheet member.

In contrast, in the radiation detection cassette 1 of the presentembodiment, the alloy containing Mg and Li is used as a material of theback housing part 12. Thus, EMC is improved compared to a case where therelated-art Mg alloy is used. Hence, it is not necessary to provide thesheet member as in the related-art radiation detection cassette, and asillustrated in FIG. 12, a medium plate 80 serving as the support membercan be arranged near the opening 12 e. The medium plate 80 is formed ofmetal. It is preferable that a gap d2 between the opening 12 e and themedium plate 80 is more than 0 mm and 2 mm or less.

Additionally, the alloy of the back housing part 12 instead of theprotective film 30 may be made to contain Ca. It is preferable that thecontent of Ca is 0.3 mass % or more and 7 mass % or less. By making thecontent of Ca be 0.3 mass % or more, flame retardance can be improved.Additionally, the weight reduction can be achieved by making the contentof Ca be 7 mass % or less. As the alloy containing Ca, for example, analloy of 14 mass % of Li, 9 mass % of Al, 1 mass % of Ca, and 76 mass %of Mg can be used.

Additionally, both the alloy of the back housing part 12 and theprotective film 30 may be made to contain Ca.

Additionally, it is preferable that the radiation detection cassette 1of the above embodiment includes the frame body 13. However, asillustrated in FIG. 13, it is preferable that the frame body 13 isformed so as to protrude further outward than a position (a positionillustrated by a dotted line in FIG. 13) at a side end of the backhousing part 12 as seen from the radiation exposure side. By adoptingsuch a configuration, for example, the impact resistance when theradiation detection cassette 1 has fallen on the ground can be improved.

Additionally, as a method of improving the impact resistance of theradiation detection cassette 1, in a case where the protective film 30is formed of the paint film, it is preferable that a cushioning propertyis provided by making the paint thickness be 50 μm or more.Additionally, two or more layers of paint films may be formed, and thetotal thickness thereof may be 50 μm or more. Additionally, in a casewhere the resin sheet is used as the protective film 30, it ispreferable to use a resin sheet of 50 μm or more.

Additionally, regarding the protective film 30 of the radiationdetection cassette 1 of the above embodiment, it is preferable toperform water-repellent coating processing or water-repellent painting.Accordingly, the corrosion resistance can be further improved.

Explanation of References

-   -   1: radiation detection cassette    -   2: radiation detector    -   10: housing    -   11: transmission plate    -   12: back housing part    -   12 a: side peripheral surface part    -   12 b: battery housing part    -   12 c: female thread part    -   12 d: rib    -   12 e: opening    -   12 f: recess    -   13: frame body    -   13 a: female thread part    -   13 b: outer surface    -   15: male thread    -   16: battery    -   17: male thread    -   18: insertion screw    -   20: radiation detector    -   21: scintillator layer    -   22: active-matrix substrate    -   30: protective film    -   31: first protective film    -   31 a: end part    -   32: second protective film    -   32 a: end part    -   40: radiation shield plate    -   50: support    -   60: radiation shield    -   61: housing part    -   62: radiation shield plate    -   63: attachment member    -   63 a: turning shaft    -   70: waterproof structure    -   80: medium plate    -   d1: gap    -   d2: gap

What is claimed is:
 1. A cassette having a transmission plate disposedon radiation exposure side and transmitting radiation, and a housingpart disposed on opposite to the radiation exposure side, the cassettecomprising: a radiation detector that is disposed between thetransmission plate and the housing part, wherein material of the housingpart contains 5 mass % or more and 25 mass % or less of lithium.
 2. Thecassette according to claim 1, wherein the housing part has recesses ona surface on the radiation detector side.
 3. The cassette according toclaim 1 further comprising: a radiation shield plate that is provided onthe side opposite to the radiation exposure side with respect to theradiation detector; and a support that is provided on the side oppositeto the radiation exposure side with respect to the radiation shieldplate, and that supports the radiation shield plate, wherein the supportis fixed to the housing part.
 4. The cassette according to claim 1further comprising: a support that is provided on the side opposite tothe radiation exposure side with respect to the radiation detector, andthat supports the radiation detector, wherein the support is fixed tothe housing part, and wherein the support and the housing part directlyface each other.
 5. The cassette according to claim 1, wherein thematerial of the housing part further contains aluminum.